Tooling and hardware
Woodruff key chart: key sizes, keyseats and cutters
Key 808 is 8/32 = 1/4 in wide on an 8/8 = 1 in diameter, and it is cut with a #808 keyseat cutter. Woodruff keys 204 to 1212 per ASME B17.2 (Woodruff keys and keyseats), full radius type.
Technical review pending. Formulas and values are cited. This notice comes down after a machinist review.
Source: ASME B17.2 (Woodruff keys and keyseats); key dimensions as published by National Machine Tool Co. and a fastener distributor's ANSI B17.2 data sheet; keyseat depths from W.M. Berg Woodruff key data; cutter sizes from ICS Cutting Tools catalog data; Machinery's Handbook (keyseat depth and chordal height).
| Key no. | Width W (in) | Diameter D (in) | Key height C max (in) | Key height C min (in) | Key length max (in) | Shaft keyseat depth B (in) | Hub keyway depth (in) | Cutter, D x W and shank (in) |
|---|---|---|---|---|---|---|---|---|
| 204 | 1/16 (0.0625) | 1/2 (0.5000) | 0.203 | 0.198 | 0.491 | 0.1668 | 0.0372 | #204, 1/2 x 1/16, 1/2 shank |
| 304 | 3/32 (0.0938) | 1/2 (0.5000) | 0.203 | 0.198 | 0.491 | 0.1511 | 0.0529 | #304, 1/2 x 3/32, 1/2 shank |
| 404 | 1/8 (0.1250) | 1/2 (0.5000) | 0.203 | 0.198 | 0.491 | 0.1355 | 0.0685 | #404, 1/2 x 1/8, 1/2 shank |
| 305 | 3/32 (0.0938) | 5/8 (0.6250) | 0.250 | 0.245 | 0.612 | 0.1981 | 0.0529 | #305, 5/8 x 3/32, 1/2 shank |
| 405 | 1/8 (0.1250) | 5/8 (0.6250) | 0.250 | 0.245 | 0.612 | 0.1825 | 0.0685 | #405, 5/8 x 1/8, 1/2 shank |
| 505 | 5/32 (0.1563) | 5/8 (0.6250) | 0.250 | 0.245 | 0.612 | 0.1669 | 0.0841 | #505, 5/8 x 5/32, 1/2 shank |
| 605 | 3/16 (0.1875) | 5/8 (0.6250) | 0.250 | 0.245 | 0.612 | Not listed | Not listed | #605, 5/8 x 3/16, 1/2 shank |
| 406 | 1/8 (0.1250) | 3/4 (0.7500) | 0.313 | 0.308 | 0.740 | Not listed | Not listed | #406, 3/4 x 1/8, 1/2 shank |
| 506 | 5/32 (0.1563) | 3/4 (0.7500) | 0.313 | 0.308 | 0.740 | Not listed | Not listed | #506, 3/4 x 5/32, 1/2 shank |
| 606 | 3/16 (0.1875) | 3/4 (0.7500) | 0.313 | 0.308 | 0.740 | Not listed | Not listed | #606, 3/4 x 3/16, 1/2 shank |
| 806 | 1/4 (0.2500) | 3/4 (0.7500) | 0.313 | 0.308 | 0.740 | Not listed | Not listed | #806, 3/4 x 1/4, 1/2 shank |
| 507 | 5/32 (0.1563) | 7/8 (0.8750) | 0.375 | 0.370 | 0.866 | Not listed | Not listed | #507, 7/8 x 5/32, 1/2 shank |
| 607 | 3/16 (0.1875) | 7/8 (0.8750) | 0.375 | 0.370 | 0.866 | Not listed | Not listed | #607, 7/8 x 3/16, 1/2 shank |
| 707 | 7/32 (0.2188) | 7/8 (0.8750) | 0.375 | 0.370 | 0.866 | Not listed | Not listed | #707, 7/8 x 7/32, 1/2 shank |
| 807 | 1/4 (0.2500) | 7/8 (0.8750) | 0.375 | 0.370 | 0.866 | Not listed | Not listed | #807, 7/8 x 1/4, 1/2 shank |
| 608 | 3/16 (0.1875) | 1 (1.0000) | 0.438 | 0.433 | 0.992 | Not listed | Not listed | #608, 1 x 3/16, 1/2 shank |
| 708 | 7/32 (0.2188) | 1 (1.0000) | 0.438 | 0.433 | 0.992 | Not listed | Not listed | #708, 1 x 7/32, 1/2 shank |
| 808 | 1/4 (0.2500) | 1 (1.0000) | 0.438 | 0.433 | 0.992 | Not listed | Not listed | #808, 1 x 1/4, 1/2 shank |
| 1008 | 5/16 (0.3125) | 1 (1.0000) | 0.438 | 0.433 | 0.992 | Not listed | Not listed | #1008, 1 x 5/16, 1/2 shank |
| 1208 | 3/8 (0.3750) | 1 (1.0000) | 0.438 | 0.433 | 0.992 | Not listed | Not listed | #1208, 1 x 3/8, 1/2 shank |
| 609 | 3/16 (0.1875) | 1 1/8 (1.1250) | 0.484 | 0.479 | 1.114 | Not listed | Not listed | #609, 1 1/8 x 3/16, 1/2 shank |
| 709 | 7/32 (0.2188) | 1 1/8 (1.1250) | 0.484 | 0.479 | 1.114 | Not listed | Not listed | #709, 1 1/8 x 7/32, 1/2 shank |
| 809 | 1/4 (0.2500) | 1 1/8 (1.1250) | 0.484 | 0.479 | 1.114 | Not listed | Not listed | #809, 1 1/8 x 1/4, 1/2 shank |
| 1009 | 5/16 (0.3125) | 1 1/8 (1.1250) | 0.484 | 0.479 | 1.114 | Not listed | Not listed | #1009, 1 1/8 x 5/16, 1/2 shank |
| 610 | 3/16 (0.1875) | 1 1/4 (1.2500) | 0.547 | 0.542 | 1.240 | Not listed | Not listed | #610, 1 1/4 x 3/16, 1/2 shank |
| 710 | 7/32 (0.2188) | 1 1/4 (1.2500) | 0.547 | 0.542 | 1.240 | Not listed | Not listed | #710, 1 1/4 x 7/32, 1/2 shank |
| 810 | 1/4 (0.2500) | 1 1/4 (1.2500) | 0.547 | 0.542 | 1.240 | Not listed | Not listed | #810, 1 1/4 x 1/4, 1/2 shank |
| 1010 | 5/16 (0.3125) | 1 1/4 (1.2500) | 0.547 | 0.542 | 1.240 | Not listed | Not listed | #1010, 1 1/4 x 5/16, 1/2 shank |
| 1210 | 3/8 (0.3750) | 1 1/4 (1.2500) | 0.547 | 0.542 | 1.240 | Not listed | Not listed | #1210, 1 1/4 x 3/8, 1/2 shank |
| 811 | 1/4 (0.2500) | 1 3/8 (1.3750) | 0.594 | 0.589 | 1.362 | Not listed | Not listed | #811, 1 3/8 x 1/4, 1/2 shank |
| 1011 | 5/16 (0.3125) | 1 3/8 (1.3750) | 0.594 | 0.589 | 1.362 | Not listed | Not listed | #1011, 1 3/8 x 5/16, 1/2 shank |
| 1211 | 3/8 (0.3750) | 1 3/8 (1.3750) | 0.594 | 0.589 | 1.362 | Not listed | Not listed | #1211, 1 3/8 x 3/8, 1/2 shank |
| 812 | 1/4 (0.2500) | 1 1/2 (1.5000) | 0.641 | 0.636 | 1.484 | Not listed | Not listed | #812, 1 1/2 x 1/4, 1/2 shank |
| 1012 | 5/16 (0.3125) | 1 1/2 (1.5000) | 0.641 | 0.636 | 1.484 | Not listed | Not listed | #1012, 1 1/2 x 5/16, 1/2 shank |
| 1212 | 3/8 (0.3750) | 1 1/2 (1.5000) | 0.641 | 0.636 | 1.484 | Not listed | Not listed | #1212, 1 1/2 x 3/8, 1/2 shank |
W and D show the fraction and its decimal to 4 places. Key heights and lengths as published, to 3 places; depths to 4 places. Not listed means no keyseat depth is published here yet; take B from the drawing or ASME B17.2. Every cutter listed is on a 1/2 in shank.
Values are for full radius Woodruff keys per ASME B17.2; check the key and keyseat against the drawing before cutting.
How to read the key number
808: the last two digits, 08, are the diameter in eighths: 8/8 = 1 in. The digits before, 8, are the width in thirty-seconds: 8/32 = 1/4 in. So 808 is 1/4 x 1 in. 1210 is 12/32 = 3/8 in wide on 10/8 = 1 1/4 in. 204 is 2/32 = 1/16 in wide on 4/8 = 1/2 in.
Woodruff keyseat depth
Depth of cut from the top of the shaft
in
depth = Y + B = 0.0052 + 0.1355 = 0.1407 in
Center the cutter on the shaft, touch off on the top, then feed down this far.
Chordal height Y
in
Y = (Ds - sqrt(Ds^2 - W^2)) / 2 = (0.75 - sqrt(0.75^2 - 0.125^2)) / 2 = 0.0052 in
Key size W x D
in
W = n_w / 32 = 4 / 32 = 0.1250 in; D = n_d / 8 = 4 / 8 = 0.5000 in
Key height C max 0.203 in. Cutter #404, 1/2 x 1/8 in, 1/2 in shank.
How it works
W = n_w / 32; D = n_d / 8; Y = (Ds - sqrt(Ds^2 - W^2)) / 2; depth = Y + B
| Symbol | Meaning | Unit |
|---|---|---|
| n_w | Digits before the last two of the key number | none |
| n_d | Last two digits of the key number | none |
| W | Key width, also the cutter width | in |
| D | Nominal key diameter, also the cutter diameter | in |
| Ds | Shaft diameter | in |
| B | Shaft keyseat depth, from the table or the drawing | in |
| Y | Chordal height: shaft surface above the keyseat edge | in |
| C | Key height at full radius | in |
B is measured at the keyseat side wall. The top of a round shaft sits Y above that wall, so the cutter feeds Y + B from first touch. The chordal height formula is the same one the keyway dimensions chart uses for square keys.
Worked example: key 404 on a 0.750 in shaft
Key 404, Ds = 0.750 in, B = 0.1355 in from the table.
- W = 4 / 32 = 0.1250 in; D = 4 / 8 = 0.5000 in.
- Y = (0.750 - sqrt(0.5625 - 0.015625)) / 2 = (0.750 - sqrt(0.546875)) / 2 = (0.750 - 0.739510) / 2 = 0.005245 in, shown 0.0052 in.
- Depth from top = 0.005245 + 0.1355 = 0.140745 in, shown 0.1407 in.
Result: feed 0.1407 in from the top of the shaft with a #404, 1/2 x 1/8 in cutter.
Worked example: key 505 on a 1.000 in shaft
Key 505, Ds = 1.000 in, B = 0.1669 in from the table.
- W = 5 / 32 = 0.15625 in, shown 0.1563 in; D = 5 / 8 = 0.6250 in.
- Y = (1.000 - sqrt(1.000 - 0.024414)) / 2 = (1.000 - sqrt(0.975586)) / 2 = (1.000 - 0.987718) / 2 = 0.006141 in, shown 0.0061 in.
- Depth from top = 0.006141 + 0.1669 = 0.173041 in, shown 0.1730 in.
Result: feed 0.1730 in from the top of the shaft with a #505, 5/8 x 5/32 in cutter.
Spot checks against the sources
- 204: W 1/16 in, D 1/2 in (decoded); key height 0.203 in max (two published key charts agree); B 0.1668 in, hub depth 0.0372 in (Berg data); cutter #204, 1/2 in diameter, 1/16 in face, 1/2 in shank (ICS catalog data, a second cutter listing agrees).
- 1212: W 12/32 = 3/8 in, D 12/8 = 1 1/2 in (decoded); key height 0.641 in max, 0.636 in min; key length 1.484 in max (two published key charts agree); cutter #1212, 1 1/2 in diameter, 3/8 in face (ICS catalog data).
Shop notes
- The cutter number is the key number: a #808 cutter is 1 in diameter and 1/4 in wide.
- Some cutters run a little over nominal diameter: one maker lists #204 at 0.510 in and #812 at 1.515 in cutting diameter. Read the cutter, not the number, if the keyseat length matters.
- Center the cutter on the shaft, touch off on the top of the shaft, then feed Y + B. Check the depth with the key in place: it should stand above the shaft a little less than the hub keyway depth, so the hub clears the top of the key.
- Key height and depth values are the standard's; the drawing governs.
FAQ
What do the numbers on a Woodruff key mean?
The last two digits are the diameter in eighths of an inch, the digits before are the width in thirty-seconds. 808 is 1/4 x 1 in.
What size is a 1212 Woodruff key?
3/8 in wide (12/32) on a 1 1/2 in diameter (12/8), 0.641 in tall at most.
Which cutter cuts a 404 Woodruff keyseat?
A #404 cutter: 1/2 in diameter, 1/8 in wide, on a 1/2 in shank.
How deep is the keyseat for a 404 key?
0.1355 in (B per ASME B17.2), plus the chordal height when you touch off on the top of the shaft: 0.1407 in on a 0.750 in shaft.
What is the difference between a Woodruff key and a square key?
A Woodruff key is a half-round disk that sits in a curved keyseat cut by a plunge cutter; a square key sits in a straight keyseat. Square and rectangular keys are on the keyway dimensions chart, sized by shaft diameter.
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